Biocontrol of phytopathogenic fungi by Bacillus spp.: Strain screening, regulatory mechanisms, and field application

Bacillus species, which are among the most extensively studied and widely used rhizobacteria, have demonstrated potent antagonistic activity against a broad spectrum of phytopathogenic fungi, making them ideal microorganisms for biological control. Phytopathogenic fungi cause severe preharvest and postharvest losses in global crop production, significantly reducing yield and quality. The prolonged and heavy reliance on traditional chemical fungicides has resulted in environmental pollution and poses risks to human health. In this context, Bacillus-based biological control has emerged as an environmentally friendly, cost-effective, and sustainable alternative strategy. In this review, we provide a comprehensive overview of the screening of Bacillus strains for the biocontrol of phytopathogenic fungi. The possible mechanisms, including the production of a wide array of antifungal metabolites, the induction of systemic resistance in host plants, and indirect suppression through competition for nutrients and space, were also evaluated. Furthermore, the effects of multistrain synergistic consortia and the development of multifunctional Bacillus strains on biocontrol efficacy are discussed, and research advances in the application of Bacillus spp. in the control of soilborne diseases and phytopathogenic fungi are summarized. Finally, this review provides suggestions for the development of efficient Bacillus-based biocontrol agents, thereby promoting sustainable agricultural development.